The primary goal of this project is to prepare high purity Factor V and study its biochemical characteristics and the mode of its conversion to its activated form, Factor Va. Both bovine blood plasma and human plasma will be used as sources of the Factor V. Attention will be directed to a study of the preparation of antibodies to Factor V and Factor VA. In addition, the nature of the interaction of specific types of phospholipids with Factor V and Factor Va through use of highly purified phospholipids and also short chain synthetic substrates will be explored. It is hoped that specific sites for the interaction of these lipids with Factor V and Va can be identified through specific cleavage procedures and isolation of lipid containing fragments. The differences in the degree of activation of bovine plasma Factor V obtained from blood collected by venipuncture compared to that collected from the slaughter house will be investigated and will be compared to that seen with human plasma Factor V. In the latter instance it is highly possible that a different form of Factor V is found in venipuncture blood than noted in the slaughter house preparations. Concomitantly the nature of the conversion of Factor V to Factor Va will be studied in detail.